Best Oil For Mercedes Diesel Engines

Both gas and diesel engine oils are created by blending the additives and the base oil to create a mixture that offers specific performance characteristics. The difference is the fact that diesel motor oils usually consist out of more additives, and are higher in viscosity.

Most Mercedes diesel engines use 5W-30 synthetic oil grades, and some of them use different viscosity oil blends such as 10W-40 for engines that operate in different temperature ranges and are usually older than the ones using 5W-30.

Difference between gas and diesel motor oils

The differences mostly consist out of different viscosity properties and a difference associated with the number of additives inside the oils.

But the difference does not stop there, as modern-day Mercedes diesel engines have a catalytic converter that is designed to filter out the toxic emissions before they enter the atmosphere. Motor oils found in most modern Mercedes models have a higher anti-wear (AW) load in regards to ZDDP or zinc dialkyl dithiophosphate.

The difference is the fact that the converters found in modern-day diesel engines are specifically designed to deal with this issue, and the converters found in a gas-engined car are not. This is the primary reason why one should never use diesel motor oil for a gas-engined car.

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Most diesel engines usually use motor oil that is higher in viscosity. And choosing the right viscosity is vital for proper engine function. If you put higher viscosity oil inside a gasoline engine, you might end up with higher operating temperatures due to fluid friction which can significantly shorten the lifespan of the engine.

Additive levels in diesel motor oils

Different additive levels are what greatly separates diesel and gas motor oils. This is mostly because diesel engines create more combustion by-products. For such purposes, a diesel motor oil consists out of a lot more detergent additives that are there to clean the engine.

But if you use such oil in a gasoline-powered car you’ll experience a drastic decrease in performance. Diesel motor oils with increased levels of additives usually decrease the compression ratio of an engine, and can further decrease the efficiency as well.

Check the package labels to make sure. A clear way to tell is the API (American Petroleum Institute) badge on the label. On this badge, you will see a designation that starts with a ‘’C’’ which indicates a diesel engine motor oil, or an S which would indicate a gas engine motor oil.

Engine oil for larger Mercedes diesel engines

Mercedes uses heavy-duty diesel engines in many commercial and some non-commercial vehicles. For such engines, higher viscosity oil levels are advised as these engines usually work harder than your average C220 engine.

15W-40 or 10W-30 are usually the levels of viscosity associated with these engines.  It depends on the temperature levels these engines usually operate. You should always consult with a professional when it comes to motor oil types as a professional is able to consider all the variables associated with your specific usage scenario.

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It is also not advisable to mix different brands of motor oil because the analysis surrounding a certain product does not include the oil effectiveness levels if mixed with a different brand. Keeping your engine oil topped off at all times is the most important aspect of them all.

FAQ Section

How often should you do an oil change on a diesel engine?

It depends on where and how you use your car. If you are predominantly using it on the highway, your motor oil can last longer, if you use your car in shorter trips mostly associated with city driving, your engine oil is going to degrade a lot faster.

No matter the case, you should replace your motor oil every 5000 or so miles, in that way you are sure to always have a properly lubricated engine. Changing the oil filters with the oil itself is also highly advisable, at least every 7500 miles.

You should follow the maintenance schedules associated with a specific automaker. For example, most Mercedes models have an A and a B service, and both of these consist out of replacing the oil.

Why do diesel engines require more oil?

Gas and diesel engines are designed differently, and most diesel engines usually have a larger bearing size as compared to a gas-powered engine. That means that there is more surface that needs lubricating as compared to a gas-powered engine.

Diesel engines are internally harder to keep clean, they offer larger motor oil tank sizes, and motor oil used in diesel engines is sometimes used for cooling the engine itself.

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The main reason why diesel engines use more oil is the fact that the oil in a diesel engine serves as a vital part of the compression system compared to a gas engine, and such levels are necessary for comparable oil change intervals.

Does my engine oil impact my fuel efficiency?

Yes, it does. Improper motor oil usage can lead to many unwanted consequences, ranging from bad fuel economy and decreased performance up to a shorter engine life span and increased wear and tear of the internal engine components.

Lower viscosity oils usually offer a thinner layer between the moving parts of the engine which decreases the friction between the parts. This allows the engine to be more efficient, thus the favorable fuel economy.

Thicker viscosity oils create a thicker layer between the moving parts that further increase the friction between those parts, which in turn lowers the fuel efficiency, but keeps the engine safer and better lubricated.

How does cold affect motor oil?

Cold temperatures affect motor oil quite a bit, especially at start-up. Motor oil becomes a lot thicker in cold weather which makes the oil a lot harder to flow. This can put a serious strain on your engine and further increase wear and tear.

Engine motor oil viscosity levels should be lower in winter times as they will always flow a lot easier. So choosing a 0W-20 over a 10W-30 motor oil is recommended.

Marko Mikulic

Why do you love writing about cars? I love writing about cars as cars are a huge personal interest of mine. I was raised in a car enthusiast community and ever since I was young, I always wanted to do car-related work.

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